Studies are being conducted on events leading to the onset of various ocular diseases and on methods for their potential pharmacological control. The relationships between the enzymes aldose reductase and aldehyde reductase and the progression of ocular complications such as retinopathy, cataract, pupil function and iris changes, and keratopathy induced by diabetes or galactosemia are being investigated. Methods for either delaying or preventing the onset of these complications through the pharmacological control of aldose reductase are also being developed. Events leading to the formation of several types of cataracts are also being studied as well as methods for controlling the onset of these cataracts through pharmacological intervention.